Bottom sheet feeder using separation belt and retard pad

ABSTRACT

A sheet separation belt is positioned at the bottom of a stack in a cut-away in the tray carrying the stack. The belt is carried by three rollers. One is located a distance from the edge of the stack. Another is located near the stack edge. A retard pad is biased against the belt between the second and third rollers. An infeed chute abutts or restrains the lead edge of the stack and is sloped to slope the stack. The slope generates a normal component between the stack and belt that enhances the feeding engagement. A blade is employed to clean contaminants from the belt.

" United States Patent Kramell et al.

[451 July 22,1975

[54] BOTTOM SHEET FEEDER USING SEPARATION BELT AND RETARD PAD [75] Inventors: Hans P. Kramell, Perry; Richard C.

Hansen, Penfield, both of NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Mar. 19, 1973 [21] Appl. No.: 342,653

[52] U.S. Cl 271/35; 271/167 [51] Int. Cl B65h 3/04 [58] Field of Search 271/35, 34, 160, 167; 198/230 [56] References Cited UNITED STATES PATENTS 707,220 8/1902 Eylar 271/35 1,018,060 2/1912 .lahn 271/35 2,551,123 5/1951 Heller 198/230 3,219,339 11/1965 Gutierrez 271/34 X 3,239,213 3/1966 Griswold 271/35 Primary Examiner-Richard A. Schacher Assistant Examiner-Bruce H. Stoner, Jr.

[57] ABSTRACT A sheet separation belt is positioned at the bottom of a stack in a cut-away in the tray carrying the stack. The belt is carried by three rollers. One is located a distance from the edge of the stack. Another is located near the stack edge. A retard pad is biased against the belt between the second and third rollers. An infeed chute abutts or restrains the lead edge of the stack and is sloped to slope the stack. The slope generates a normal component between the stack and belt that enhances the feeding engagement. A blade is employed to clean contaminants from the belt.

1 Claim, 1 Drawing Figure BOTTOM SHEET FEEDER USING SEPARATION BELT AND RETARD PAD BACKGROUND OF THE INVENTION This invention relates to sheet feeding method and apparatus. More specifically, the present invention relates to a sheet feeder for a facsimile transceiver which is able to feed original documents from a stack when the transceiver is in a send mode and specially coated copy sheets when the transceiver is in a receive mode.

The present sheet feeder is of the type disclosed in copending application Ser. No. 225,513, filed Feb. 1 1, 1972 in the name of Klaus K. Stange and assigned to the present assignee, now U.S. Pat. No. 3,768,803. The sheet feeding method and apparatus of the copending application are expressly incorporated in this application. The present sheet feeder is especially suited for facsimile machines operating on thermoelectric paper of the type described in U.S. Pat. No. 2,555,321, the disclosure of which is incorporated herein. The thermoelectric, paper may include a thermoplastic coating or the like to prevent curling located onthe side that is gripped by the sheet feeding mechanism. The thermoplastic coating offers a low energy surface that is slipperyl.making the sheets hard to feed.

Bottom sheet feeding of documents and copy sheets to a facsimile machine is advantageous for compactness. A facsimile feeder of this type is disclosed in copending application Ser. No. 253,721, filed May 16, 1972, now U.S. Pat. No. 3,790,159, issued Feb. 5, 1974, assigned to the present assignee. The disclosure of this facsimile application is also expressly incorporated herein. Bottom sheet feeding is inherently difficult in any environment. One reason for the difficulty in the facsimile environment is the above-mentioned slippery nature of the copy sheets. Another reason for the difficulty is the normal force between the stack and'feeder effecting the frictional engagement for separation of the bottom'most sheet from the stack.

The normal force problem sometimes is cured 'by placing a weight on top of the stack, but this is metalways an adequate solution since stack weight is often substantial and of course decreases as the stack is depleted. A complex spring arrangement or equivalent mechanism could be used to force the stack against the feeder but such solutions are usually too expensive, at least in terms of space, when compactness is essential as with the system disclosed in the above facsimile application.

Accordingly, it is an object of the current invention to overcome the above-noted difficulties in feeding sheets from a stack.

Another object of the present invention is to enhance the effectiveness of sheet feeders operating in a bottom sheet feeding mode of the type including a separation belt for grasping a sheet near the edge of a stack and pullingthe sheet through a queuing throat formed by a retard pad biased against an unsupported length of the belt.

Yet another object of the invention at hand is to prevent misfeeds and multiple feed of sheets from a stack to a facsimile transceiver. This means successfully feeding sheets of diverse composition, shape and condition to the transceiver when in a transmit mode and copy sheets with surfaces that make frictional engagement difficult to the transceiver when in a receive mode.

Still another object of this invention is the maintenance of a generally constant normal force between the stack and feeder during feeding from the bottom of a stack or the equivalent thereof.

A further object of the invention is to improve belt feeders by employing a blade member to clean the separation belt of contaminants.

The above and other objects of the current invention are realized using, in a bottom sheet configuration, a separation belt positioned to contact the bottom most sheet in a stack for pulling the sheet into a queuing throat formed by biasing a retard pad against an unsupported sectionof the belt. The invention of hand distinguishes over the Stange feeder supra as well as those of the prior art including that disclosed in the Sturtevant U.S. Pat. No. 664,340 (1900), the Wells U.S. Pat. No. 1,167,367 (1916), the VanDalen U.S. Pat. No. 3,108,801 (1963) and the Lindquist U.S. Pat. No. 3,485,489 (1969). The distinquishing features include the facsimile environment, the composition of the sheets being fed, means for increasing frictional en gagement, means for establishing a normal force with a feeder and means for maintaining that normal force.

The instant feeder includes a retard pad and separator belt carried by three belt support means or roller members. Adjacent the retard pad is an infeed chute which is at an angle relative to the separation belt giving rise to a normal force between the belt and stack when the belt is moving in the feed direction. The retard pad and infeed chute are mounted on a cantilevered member protruding over the stack. A weight is pivoted at the free end of the cantilever to simulate stack weight for feeding the last few sheets in a stack. Because the weight is pivoted it does not interfere with the insertion or withdrawal of a stack. The cantilever is rigidly fixed during feeding to bias the retard pad and belt against one another. The cantilever is rotatable about its fixed end to move the pad and chute out of the way to clear the area or bypass the feeder as might be desired when a single sheet is all that is being advanced to a transceiver or the like. One heretofore unknown and unappreciated element of this invention includes the third roller member placed near the edge of the stack and assisting in the biasing of the belt and retard pad against one another. Another such element is the angled infeed chute.

DESCRIPTION OF THE DRAWING Other objects and features of the present invention will be'apparent from the foregoing and a further reading. In addition, other objects and features will be apparent from the drawing taken alone or in combination with the description. The drawing is a schematic, sideelevation view of the instant sheet feeder in sheet feeding engagement with a stack. The thicknesses of the sheets and the sizes of the components are not to scale and in some cases are exaggerated for clearer understanding.

DETAILED DESCRIPTION The feeder of this invention is intended primarily for bottom feeding of comparatively small stacks composed of not greater than about to 200 sheets. It is designed to serve relatively low volume recorders such as employed in facsimile transceivers operating in the 1-6 minute per 8 /2 X 1 1 inch page speed range. The feeder must be compact and handle both documents and copy paper. The documents often include 20 pound bond paper and the ruffled physical shape of the documents and contaminants on them give rise to irregular stacks rendering sheet feeding very difficult. In addition, the thermoelectric paper of the type described in US. Pat. No. 2,555,321 mentioned at the outset, is more slippery on the non-recording side because of a thermoplastic coating, e.g., plastisol, or other suitable stiffening material such as protein that is capable of increasing the beam strength of a sheet. This tends to dietate that sheets be fed from the less slippery side, (i.e., the side having the greater coefficient of friction, and- /or having a lower surface energy state). However, packaging considerations may dictate that the sheet feeder be positioned relative to the stack and the transceiver such that the more slippery side be engaged by the feeder. This is the situation with the facsimile system in the above-mentioned application, Ser. No. 253,721.

The present feeder is non-obvious for several reasons including the fact that it is able to operate on the above noted sheets from the wrong or more slippery sheet surface. The disparity in surface friction shows up further in the queuing throat. The queuing throat is the region formed between a retard means and a separation belt. The separation belt and retard means type of feeder normally require that the frictional force between the belt and outermost sheet in a stack be greater than the intersheet coupling forces and the frictional force between the retard means and the side of the sheet opposite that engaged with the belt. This condition is not automatically obtained when thermoelectric sheets or the like are fed with the slippery surface of the sheet facing the separation belt.

Turning to the drawing, the feeder includes the continuous elastic belt 11 and the synthetic rubber retard pad 12. A stack of sheets 15 is carried by the tray 16 and has its lead edge profiled to an angle of about 50 relative to the belt by the sloped infeed chute 17. The edge of the stack is profiled or sloped when the belt moves in the direction of sheet feed. The moving belt carries the stack against the chute and the incline or angle of the chute generates a force vector normal to the belt. This normal force enhances the feeding. Chute angles of 40 to 60 are satisfactory with the 50 angle presently being preferred.

The separation belt is carried by three belt support means including the left idler roller or pulley 20, the intermediate idler roller 21 and the driven roller or pulley 22. The shaft of roller 22 is coupled by appropriate drive means for effecting movement of the belt 11 around the rollers in the direction of sheet feed. The scraper blade 25 is a stiff member biased against belt 11 to scrape off dirt particles, paper fibers and other contaminants adhering to the belt. The blade includes a relatively sharp edge which is oriented against the direction of belt travel so as to bite into the belt for good cleaning action. The blade does minimal damage to the belt 11 while performing the cleaning action because it is biased against the belt in an unsupported belt region. Consequently, the belt can flex or stretch when necessary. Furthermore, because feeder 10 is designed for comparativelyflow volume sheet feeding operations, the blade has 'iro substantial detrimental effect on belt life. I

The retardiimeans or pad 12 is fixedly coupled to the cantilever me'r nber 31. The infeed chute is also carried by the cantilever and comprises a metal sheet or plate extending transversely to the stack a distance adequate to profile the stack. The profiling or sloping of the lead edge of the stack is accomplished after the operator inserts a stack into the tray and the separation belt moves in the direction of feed as discussed above. The entrance 36 to the queuing throat is substantially straight or linear to avoid any notches or the like in which the edges of sheets can be trapped.

The free end 32 of the cantilever extends over the stack and is of a height above the tray to more than adequately accommodate the maximum stack height. The weight 33 is pivotedly suspended from the free'end and rests on the top of the stack. This weight isnot intended to significantly affect the normal force between the" stack 15 and the beltll. Weight 33 is present so the last few sheets in a stack have some external compo} nent exerted on them to enhance feeding engagement with the separation belt. The weight is shaped in the form of the letter L and pivoted near the end of the short leg of the L in order that the weight will not interfere with the insertion or the withdrawal of sheets from the tray vl6.

The fixed end 34 of the cantilever is normally locked against movement. The result is that the retard pad is held biased against the separation belt. The fixed end can be unlocked, however, and the entire cantilever can be pivoted upward to allow access to the region around the queuing throat.

The intermediate. roller 21 is positioned under the stack near the edge and supports the belt in a manner enabling the retard pad to be biased against the belt near the stack edge to form the sheet queuing throat. The Stange application supra should be consulted for a detailed description of the queuing throat operation. It is enough here to say that multiple sheets are not able to pass through the throat resulting in a queuing .of the sheets in their order as arranged in the stack. The throat gives rise to a seriatim feeding of sheets.

Return now to theproblem of thermoelectric or the like sheets where the belt side is more slippery than the retard side. For best operation, the moving belt must exert a greater force on a sheet than the. retard pad. To insure this condition while preserving the edge feed advantages of the feeder disclosed in the Stange application, the surface area of the separation belt making edge contact is increased by extending the belt a distance from the edge. The intermediate roller 21 engages the belt with the stack near the edge and the left roller 20 engages the belt with the stack at a distance further in from the edge. This means the surface area for engagement between the belt and stack is increased compared to that in feeders like the Stange feeder thereby permitting more feeding engagement between the belt and the outermost sheet in the stack.

In addition, the 50 degree slope to, the infeed chute diverts the force exerted 'on the entire stack by the belt into a vertical or normal component that is substantially independent of sheet composition or of stack size. The normal force arising due to the sloped infeed chute increases thefe'eding engagement between the outermost sheet and the belt especially at a location over the intermediate roller 21. The reason for the increased feeding engagement is related to the fact that frictional force is proportional to the force normal to the surfaces in frictional engagement.

It has been observed that the feeding operation is especially successful when the normal force between the belt 11 and the retard pad 12 is adjusted from about 0.85 to 0.95 pounds. Other experimental observations have indicated that the pull through force, i.e., the force required to pull a sheet of pound bond paper through the queuing throat with the belt at rest, should be in the range of from about 2.6 pounds to about 3.0 pounds. in addition, a minimum drive-in force of 0.4 pounds has been identified as yielding superior feeding results. The drive-in force is that exerted on the trailing edge of a single sheet of material capable of stalling the sheet in the queuing throat with the belt in motion.

The width of the retard pad is very small compared to the width of a sheet. The same is true of the belt. For greater detail on their relative size see the Stange application. The tray 16 includes a cut-away portion to enable the separation belt to contact the bottom most sheets in the stack.

Any theoretical explanation of the present feeding method and apparatus given above is intended to be helpful to the understanding of the non-obviousness of the feeder. Elsewise, the structure and method described and shown in the drawing is adequate to patentably define the highly successful feeder of the instant invention. Any variations to the disclosed feeder including those suggested in the above-mentioned patents and applications, are intended to be within the scope of the present invention.

What is claimed is: 1. Sheet feeding apparatus for feeding and separating individual sheets from a stack of sheets comprising an endless sheet separation belt including a section carried in the direction of feed by at least three belt support means. said first belt support means positioned a distance from the edge of the stack and the second positioned opposite the stack near said edge with the first and second belt support means locating the belt between them for feeding engagement with said stack of sheets,

retard means including a fixedly mounted friction pad positioned adjacent said stack edge between second and third belt support means and biased against the belt to form a sheet queuing throat, and

an infeed chute adjacent said retard means and angled relative to the stack to slope the sides of the stack to create a normal force between the stack and a region of the belt adjacent the second belt support means,

said retard means and said infeed chute being carried by a cantilever member fixedly mounted to bias the retard means and belt against one another, said cantilever member extending over the stack of sheets and including a weight pivotally coupled thereto for exerting a force on the last few sheets in the stack requiring a simulation of stack weight for feeding engagement with the separation belt. 

1. Sheet feeding apparatus for feeding and separating individual sheets from a stack of sheets comprising an endless sheet separation belt including a section carried in the direction of feed by at least three belt support means, said first belt support means positioned a distance from the edge of the stack and the second positioned opposite the stack near said edge with the first and second belt support means locating the belt between them for feeding engagement with said stack of sheets, retard means including a fixedly mounted friction pad positioned adjacent said stack edge between second and third belt support means and biased against the belt to form a sheet queuing throat, and an infeed chute adjacent said retard means and angled relative to the stack to slope the sides of the stack to create a normal force between the stack and a region of the belt adjacent the second belt support means, said retard means and said infeed chute being carried by a cantilever member fixedly mounted to bias the retard means and belt against one another, said cantilever member extending over the stack of sheets and including a weight pivotally coupled thereto for exerting a force on the last few sheets in the stack requiring a simulation of stack weight for feeding engagement with the separation belt. 